1. Field of the Invention
The improved electronic article surveillance device of this invention may be generically referred to as a security tag used by retailers to prevent unauthorized removal or theft of consumer products. The electronic article surveillance device is constructed so that it may be easily attached to virtually any consumer product and is characterized by its electronic structure comprising deactivation means whereby the device may be rendered inoperative easily and efficiently without offending the customer, delaying check-out lines, or damaging the product. As described more completely hereinafter, it is the deactivation means of this device which I believe render it unique when compared with currently available such devices.
2. Description of the Prior Art
Shoplifting presently costs retailers billions of dollars annually, and is widely recognized as a pervasive and growing problem. Various techniques have been developed in the past for monitoring checkpoints, such as the exits of stores, in order to prevent the unauthorized taking of articles of merchandise out of the store or other protected areas. Some of these techniques utilize radiating electromagnetic energy which is reflected, absorbed or otherwise transformed by miniature electronic circuits embedded in or otherwise affixed to the protected articles. Many such systems have been developed wherein the circuits to be attached to the protected articles comprise only a small piece of metal of a special size and shape to form a resonant circuit. In such systems, a transmitter operates substantially continuously in the vicinity of the checkpoint at the resonant frequency of the circuits attached to the merchandise. When an article of merchandise bearing such circuit passes through the checkpoint, the circuit begins to resonate as a result of the transmitted energy, and this will result in actuation of an audible and/or visible alarm.
Of course, once a consumer item has been purchased, it is necessary either to remove or disarm the security tag so that the merchandise can be removed from the retail facility. This problem has, of course, been recognized in the prior art, and prior patent literature presents numerous examples of such security systems. For example, U.S. Pat. No. 3,500,373, describes and claims a method and apparatus for article theft detection utilizing principles of resonant circuits. However, this patent discloses no specific means for disarming the security tag, necessarily requiring removal of the tag at the point of purchase.
U.S. Pat. No. 3,624,631 discloses and claims a pilferage control system wherein a passive tuned circuit actuates the alarm. To preclude actuation of the alarm by tags on legitimately purchased merchandise, each passive tuned circuit of the '631 system is provided with a fusible link which is opened when the circuit is exposed to energy above a preselected level. Thus, upon legitimate purchase of a security tagged article, the tuned circuit is deactivated by exposing the security tag to sufficient electromagnetic energy to destroy the fusible link. In effect, this patent teaches "overloading" the circuit to achieve the desired fracture. It seems quite apparent that in order to insure deactivation of such a security tag not only would relatively high energy levels be required, but also there might even be a chance of damaging the merchandise during the deactivation process.
U.S. Pat. No. 3,810,147 discloses yet another electronic security system utilizing multi-frequency resonant tag circuits having distinct frequencies for detection and for deactivation. In other words, a second frequency is applied to the tag for the purpose of disarming it by rupturing a fusible link. This destroys the resonant properties of the tag at the detection frequency so that a deactivated tag produces no alarm when passing through a controlled area. However, in order to preclude inadvertent disarming of the tag, the fusible link of the '147 system requires relatively large power levels of the deactivating frequency, which not only increases the cost of such a system, but also may result in damage to the article carrying the security tag.
Other examples of the current state of the art for similar electronic article surveillance devices may be found in the following U.S. Letters Patent:
______________________________________ U.S. Pat. No. 3,863,244 3,913,219 3,967,161 4,021,705 4,498,076 4,567,473, and 4,728,938. ______________________________________
From a review of this prior patent literature, it can be seen that the use of parallel resonant circuits for security purposes is old and well known. Furthermore, the necessity of providing means within the circuit and/or external to the device for deactivating the device are also known. However, it can also be seen that, for the most part, in order to insure deactivation of a security tag upon legitimate purchase of the article, either the tag must be completely removed, or relatively high levels of electromagnetic radiation must be applied in close proximity to the security tag to insure its deactivation.
It is, therefore, clear that there remains a substantial need for an electronic article surveillance device wherein a deactivation means is provided so that the security tag is efficiently, economically and reliably deactivated without offending the customer, delaying check-out lines, or damaging the product to which the tag is attached.